In recent years, a window glass for vehicles, especially, a window glass for automobiles, is provided with various functions. For example, a defogger for removing fogging on a window glass or a glass antenna having functions as an antenna for e.g. an AM, FM or TV receiver, may be mentioned. The defogger removes fogging on a window glass in such a manner that an Ag paste containing Ag as the main component is fired on the surface of a glass plate, and to such a fired product of an Ag paste, an electric current is applied to warm up the glass. The glass antenna is produced in such a manner that an antenna pattern capable of receiving radio waves having various frequencies, such as AM, FM and TV, is formed on the surface of a glass plate by firing an Ag paste, and then the antenna pattern is connected to e.g. an amplifier for a radio or TV.
In order that such a defogger and a glass antenna can perform the desired functions, it is necessary to electrically connect, by means of a solder, a fired product of an Ag paste to an electronic component such as a terminal for connection to an electronic equipment provided on the interior side of a car. Heretofore, a solder containing Pb, such as a Pb—Sn—Bi—Ag type solder, has been usually used.
However, it takes a lot of troubles in treatment of the solder containing Pb at the time of disposal, and regulations against the use of a solder containing Pb are now being studied in various countries, such as ELV (End of Life Vehicles) directive or WEEE&RoHS (Waste Electrical and Electronic Equipment & Restriction of the use of certain Hazardous Substances in electrical and electronic equipment) directive in Europe. Therefore, a lead-free solder containing no Pb is desired not only for a solder to be used for e.g. an electrical equipment, but also for a solder to be used for a window glass for automobiles.
In order to comply with such a demand, a solder having a composition is disclosed wherein Ti, Al and Cu are incorporated to a solder containing Sn and Zn as the main components (see, for example, Patent Document 2). Further, a solder having a composition wherein Al, In, Ag, Cu and Zn are incorporated to a solder containing Sn as a main component (see, for example, Patent Document 2), and a solder containing Sn and Bi as the main components (see, for example, Patent Document 3) are disclosed. It is considered that such lead-free solders are, without containing Pb, capable of firmly bonding oxide materials of e.g. glass or ceramics to one another by means of the solders, and have an effect such that peeling is less likely to occur after soldering.
Patent Document 1: JP-A-2000-326088
Patent Document 2: JP-A-2000-141078
Patent Document 3: W02004/068643